1. Field of the Invention
This invention relates to apparatus for treating a movable surface with material which has been removed from a bar of such material. Preferably, the apparatus is used for coating photoconductive members with a low surface adhesion material.
2. Description of the Prior Art
Electrographic copiers typically make document reproductions by exposing an electrically charged photoconductive member to a light image of the document. The light image selectively discharges the photoconductive member to form a latent image charge pattern corresponding to the document. An oppositely charged developer material is brought into contact with the latent image to develop the image. The developed image is then transferred to a receiver sheet and fixed to the sheet by heat and/or pressure to yield the desired copy.
The developer material includes a resinous powder known as toner. If all the toner particles are not transferred to the receiver sheet, and some remain on the photoconductive member, the residual toner may be transferred to subsequent receiver sheets resulting in copies with "ghost" images or high density backgrounds. It is therefore standard practice to include apparatus for cleaning the photoconductive member immediately after image transfer.
One of the most commonly used cleaning apparatus for photoconductive members includes a rotating bristle brush which sweeps residual toner particles from a photoconductive member. Typical cleaning apparatus are shown and described in U.S. Pat. Nos. 3,615,813; 3,838,922; and 4,099,861. In practice however, toner oftentimes is not completely removed from the photoconductive member by the cleaning apparatus.
U.S. Pat. No. 3,973,843, which issued on Aug. 10, 1976 to N. R. Lindblad et al., discloses apparatus for treating a photoconductive member with a lubricant to facilitate removal of toner particles from the photoconductive member. Lubricant is applied to the imaging surface from an erodable bar either through direct contact of the bar to the imaging surface or through an intermediary fiberous web or rotating brush which erodes lubricant from the bar and carries it to the imaging surface. The Linblad et al. patent discloses the use of phthalic acid, isophthalic acid, terephthalic acid, or the metal or ammonium salts thereof as lubricating compounds.
U.S. Pat. No. 3,501,294, which issued on Mar. 17, 1970 to R. J. Joseph, refers to the treatment of the imaging surface of a photoconductive member with a solid hydrophobic metal salt of a fatty acid such as zinc stearate to promote both the transfer of toner particles from the imaging surface to receiver sheets, and the removal of toner particles from the imaging surface by cleaning devices. In U.S. Pat. No. 3,810,776, which issued May 14, 1974 to B. R. Banks et al., offset of toner to a heated fusing roll is prevented by coating the roll with an adhesion-preventing layer of an immiscible dispersion of a high viscosity, low surface tension component such as zinc or aluminum stearate or behenate and low viscosity, low surface tension component such as 50 centipoise silicone oil.
Although applicators as disclosed in the Linblad, Joseph, and Banks et al. patents do provide a relatively non-adhesive surface, they also create certain problems and impose certain limitations on the machine operation. Each of the proposed applicators employs an erodable bar for supplying lubricant to the imaging surface (or to the fusing roll in the case of Banks et al.). The lubricant bar is necessarily the width of the imaging surface. In some machines the bar may be as long as 17 inches or more. As the bar erodes, it becomes tapered. The lubricant is quite brittle, and the tapered edge of the bar is subject to chipping or crumbling as the bar wears. The crumbled pieces are a contaminant in the copier environment. It is a feature of the present invention to provide for even wear of the bar, thereby inhibiting crumbling.
Also, the presence of a lubricant bar imposes a limitation of the speed at which the photoconductive member may move. The bar erodes by being abraded into a powder by the applicator brush. Relative movement between the brush and the bar and between the brush and the imaging surface of the photoconductive member scatters the powder and creates dust in the machine environment. The greater the relative speeds at these two interfaces, the more dust is created. The speed of the photoconductive member must be kept below that which would produce an objectionable amount of dust. It is a feature of the present invention to provide for greatly increased photoconductor speed without increasing the relative speed at the brush/photoconductor and brush/bar interfaces.
The rate of material application is controlled in part by the pressure between the bar and the brush. As the bar erodes, it must be fed forward toward the brush, and complicated feeding mechanisms have been proposed by others. Gravity feed would be less complicated, but would result in a lessening of the pressure between the bar and the brush as the bar looses weight through erosion. It is a feature of the present invention to provide a simple feed mechanism for the erodable bar.